Stator for an automotive alternator

ABSTRACT

A stator for an automotive alternator is provided with good installation characteristics for stator coils and which can lower noise; the stator  8  including, a stator core  122  in which a plurality of slots  125  are formed at an inner circumference thereof and stator coils  23  which are fitted into the slots, and a rotor  6  provided inside the stator  8  so as to be capable of rotating, including, a rotor coil  15  for flowing a current to generate magnetic flux, and a pole core  16  for housing the rotor coil and forming a plurality of claw-shaped magnetic poles in accordance with magnetic flux, and, 2 slots  125  are provided for each set of stator coils, each phase and each magnetic pole and the total number of slots  125  is seventy-two (72) or more, the stator core  122  is such that a plurality of sheet-shaped magnetic members with a plurality of teeth  124  patterning the slots  125  at one side of a yoke  123  are laminated, the stator coils  23  are disposed in the slots  125 , and the stator core  122  is rounded such that the stator coils  23  become the inner side thereof and both end surfaces thereof are contacted to connect the stator core  122  in an annular shape.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to an alternator driven by aninternal combustion engine, and in particular, relates to a stator foran automotive alternator mounted in a vehicle such as a passenger car ortruck.

[0003] 2. Description of the Related Art

[0004]FIG. 8 is a sectional side elevation of a conventional automotivealternator. FIG. 9 is a front view of a stator core applied to a statorof a conventional automotive alternator. FIG. 10 is a circuit diagram ofa conventional automotive alternator. The conventional automotivealternator shown in the figures includes, a case 3 constructed from analuminum front bracket 1 and rear bracket 2, a shaft 5 with a pulley 4fixed on one end thereof provided so as to be capable of rotating insidethe case 3, a Lundell rotor 6 fixed to the shaft 5, fans 7 fixed on bothsides of the rotor 6, a stator 8 fixed to an inner wall of the case 3, aslip-ring 9 fixed on the other end of the shaft 5 for supplying electriccurrent to the rotor 6, a brush 10 for slidingly contacting theslip-ring 9, a brush holder 11 for receiving the brush 10, rectifiers 12electrically connected to the stator 8 for rectifying an alternatingcurrent produced in the stator 8 into a direct current, a heat sink 13fitted to the brush holder 11, and a regulator 14 attached to the heatsink 13 for adjusting the magnitude of the alternating voltage producedin the stator 8.

[0005] The rotor 6 includes a rotor coil 15 for flowing an electriccurrent to generate magnetic flux and a pole core 16 which houses therotor coil 15 and forms magnetic poles in accordance with magnetic flux.The pole core 16 includes, a pair of alternately meshed first pole corebody 17 and second pole core body 18. The first pole core body 17 andsecond pole core body 18 are made of iron and have claw-shaped magneticpoles 19, 20 at end portions thereof. Gaps are formed between adjacentclaw-shaped magnetic poles 19, 20 so that magnetic flux does not leakbetween the claw-shaped magnetic poles 19, 20, and also serve as coolingpassages for cooling the rotor coil 15.

[0006] The stator 8 comprises a stator core 22 and two (2) sets ofthree-phase stator coils 23, i.e. a conductor wound on the stator core22 at a phase difference of 30 degrees of electrical angle (see FIGS. 9and 10). The stator core 22 is formed in an annular shape by punchingthin steel sheets in a shape with convexo/concave portions atequidistant intervals and then lap winding or laminating the sheets.Slots 25 and teeth 24 extending in axial directions are formed in ainner portion of the stator core 22.

[0007] In the case of this example, there is provided the 2 sets ofthree-phase stator coils 23, there are twelve (12) magnetic poles of therotor 6, 2×3 phases correspond to each pole, and seventy-two (72) slots25 and teeth 24 are formed. The slots 25 are formed in theannular-shaped stator core 22 at a mechanical angle of 5 degrees (360degrees/72). At this time, since 72 slots uniformly correspond to the 12poles, the slots 25 are formed at a uniform interval of 30 degrees ofelectrical angle. The Y-Y connected two sets of three-phase stator coils23 is provided at a phase difference of 30 degrees of electrical anglein each slot 25, and is electrically connected to the rectifier 12.

[0008] In the automotive alternator constructed in this manner, electriccurrent is supplied from a battery (not shown) through the brushes 10and the slip ring 9 to the rotor coil 15, generating magnetic flux. Theclaw-shaped magnetic poles 19 of the first pole core 17 are magnetizedas north (N) poles by this magnetic flux, and those (poles 20) of thesecond pole core are magnetized as south (S) poles thereby. Meanwhile,rotational torque from the engine is transmitted through the belt andthe pulley 4 to the shaft 5, rotating the rotor 6. Thus, a rotatingmagnetic field is applied to the stator winding 23, generatingelectromotive force therein. This alternating electromotive force passesthrough the rectifiers 12 and is converted into direct current, themagnitude of the current is adjusted by the regulator 14, and thebattery is recharged.

[0009] In the above automotive alternator, there are one (1) slots 25for each (1) set of the stator coils 23, each (1) phase and each (1)magnetic pole. Magnetic field leakage is seldom formed between adjacentclaw-shaped magnetic poles 19, 20 of the rotor 6 via teeth 24 and thetime over which magnetic flux leaks to the teeth 24 is short.Accordingly, there is a only a small decrease in the effective magneticfield for the stator coils 23 occurring due to magnetic flux leakage,and surges in the magnetic flux is reduced.

[0010] Moreover, an automotive alternator similar to the one describedabove is shown in Japanese Patent Application Laid-open No. 4-26345.

[0011] In a conventional automotive alternator constructed as above,since the stator core has 72 slots, which is a lot, there is a problemin that the insertion time and installation characteristics of thestator coils 23 in the stator core 22 are poor.

[0012] Also, with the conventional automotive alternator, as shown inFIG. 11 which is an electromagnetic field analysis chart drafted by thepresent inventors (Slot opening portions (the abscissa) are spaced auniform interval of 30 degrees of electrical angle, this means that, forexample, with a mechanical angle of 24 degrees, 24 degrees and 36degrees are repeated and the interval is uneven. The ordinate showsratios of higher harmonic components of magnetomotive force in thestator with respect to a fundamental wave) when the interval of the slotopening portions is an equal 30 degrees fifth (5^(th)) and seventh(7^(th)) harmonics are not present in the magnetic flux densitywaveform. Nevertheless, eleventh (11^(th)) and thirteenth (13^(th))higher harmonic components of magnetomotive force in the stator 8 arelarge, and when 11^(th) or 13^(th) higher harmonic components ofmagnetomotive force are present in the rotor 6 there are problems inthat, surges in magnetic flux cannot be sufficiently suppressed due tointerference by the harmonic components and fluctuation in the generatedvoltage cannot be sufficiently suppressed. Moreover, magnetic attractiveforce is generated between the claw-shaped magnetic poles 19, 20 of therotor 6 and the stator 8 and causes the stator 8, case 3 and the like orthe claw-shaped magnetic poles 19, 20 of the rotor 6 resonate whichgenerates a sound that is unpleasant for passengers.

SUMMARY OF THE INVENTION

[0013] The present invention aims to solve the above problems with theconventional art and an object of the present invention is to provide astator for an automotive alternator which has good stator coilinstallation characteristics, which further has a large effect on surgesin magnetic flux and the magnetic attractive force between the statorand a rotor, and which can reduce higher harmonic components ofmagnetomotive force in the stator

[0014] According to one aspect of the present invention there isprovided a stator for an automotive alternator wherein,

[0015] in an automotive alternator including:

[0016] the stator including, a stator core in which a plurality of slotsextending in axial directions are formed at an inner circumferencethereof and two sets of three-phase stator coils which are fitted intothe slots;

[0017] a rotor provided inside the stator so as to be capable ofrotating, including, a rotor coil for flowing a current to generatemagnetic flux, and a pole core for housing the rotor coil and forming aplurality of claw-shaped magnetic poles in accordance with magneticflux, and,

[0018] 2

[0019] slots are provided for each phase of stator coils and eachmagnetic pole and the total number of the slots is 72 or more,

[0020] the stator core is such that a plurality of sheet-shaped magneticmembers with a plurality of teeth patterning the slots at one side of ayoke are laminated, the stator coils are disposed in the slots, and thestator core is rounded such that the stator coils become an inner sidethereof and both end surfaces thereof are contacted to connect thestator core in an annular shape.

[0021] According to another aspect of the present invention, a mutualinterval in the circumferential direction between a center of air gapsof adjacently formed slot opening portions is formed to be uneven.

[0022] According to yet another aspect of the present invention, theinterval of slot opening portions is a repeated electrical angle of αdegrees and (60−α) degrees, and α degrees is in a range of from 16 to 29degrees.

[0023] According to still yet another aspect of the present invention,the interval of slot opening portions is a repeated electrical angle ofα degrees and (60−α) degrees, and α degrees is in a range of from 22 to24 degrees.

[0024] According to still yet another aspect of the present invention,the interval of slot opening portions is a repeated electrical angle of24 degrees and 36 degrees.

[0025] According to still yet another aspect of the present invention,projections extending in a circumferential direction are formed on tipsthe teeth which partition the slots, and a mutual interval in thecircumferential direction between a center of air gaps of adjacent slotopening portions is varied by projecting lengths of the projections.

[0026] According to still yet another aspect of the present invention,widths of the teeth which partition the slots are uneven.

[0027] According to still yet another aspect of the present invention, acontact surfaces of the stator core connected as an annular-shape areformed by dividing a wide tooth among the teeth of uneven widths in acircumferential direction with a substantially orthogonal surface.

BREIF DESCRIPTION OF THE DRAWINGS

[0028]FIG. 1 is a perspective view for explaining a former windingstructure of a stator core applied to a stator for a automotivealternator according to the present invention.

[0029]FIG. 2 is a process sectional view for explaining a manufacturingprocess of a stator core.

[0030]FIG. 3 is a perspective view for explaining a manufacturingprocess of a stator core.

[0031]FIG. 4 is a front view of a stator core.

[0032]FIG. 5 is a partial enlarged view of a stator core.

[0033]FIG. 6 is a circuit diagram of the automotive alternator accordingto the present invention.

[0034]FIG. 7 is an enlarged view of an essential portion of a statorcore showing another example of the stator for a automotive alternatoraccording to the present invention.

[0035]FIG. 8 is a sectional side elevation of a conventional automotivealternator.

[0036]FIG. 9 is a front view of stator core applied in the stator of aconventional automotive alternator.

[0037]FIG. 10 is a circuit diagram of a conventional automotivealternator.

[0038]FIG. 11 is a chart showing higher harmonic components ofmagnetomotive force in a stator.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0039] Embodiment 1

[0040]FIG. 1 is a perspective view for explaining a former windingstructure of a stator core applied to the stator for a automotivealternator according to the present invention. FIG. 2 is a processsectional view for explaining the manufacturing process of a statorcore. FIG. 3 is a perspective view for explaining the manufacturingprocess of a stator core. FIG. 4 is a front view of a stator core. FIG.5 is a partial enlarged view of a stator core. FIG. 6 is a circuitdiagram of the automotive alternator according to the present invention.

[0041] As shown in FIG. 1, a stator core 122 according to the presentinvention is formed in a rectangular shape by laminating a predeterminednumber of sheets of a SPCC material which are sheet-shaped magneticmembers punched in a predetermined shape. A total number of seventy-two(72) teeth 124, which is the same as in the related art, are formed atone side of a yoke 123. Trapezoid-shaped slots 125 are formed betweenadjacent teeth 124.

[0042] As is shown in (a) of FIG. 2, insulators 49 are mounted in theslots 125 of the stator core 122, and straight portions of wire-strandgroups 35A, 35B are inserted in each slot 125 so as to be stacked.Accordingly, as is shown in (b) of FIG. 2, wire-strand groups 35A, 35Bare mounted in the stator core 122. At this time, straight portions 30 bof wire-strands 30 are insulated from the stator core 122 by theinsulators 49 and are received in the slots 125 so as to line up in arow in a radial direction.

[0043] Next, as is shown in FIG. 3, both end surfaces of the stator core122 are brought together and welded, and thus a cylindrical stator core122 is obtained, as shown in (c) of FIG. 2 and FIG. 4. By rounding thestator core 122, each slot acquires a rectangular cross-section andopening portions 127 thereof becomes smaller than the width dimension ofthe straight portions 30 b.

[0044]FIG. 5 is a partial enlarged view of a stator core according tothe present invention. In the present invention, although the totalnumber of slots 125 is the same as that in a conventional example, 72slots, and there are 12 rotor magnetic poles, an interval, taken fromthe center of air gaps of adjacent slot opening portions 127, in acircumferential direction, is uneven. That is, projections 124 aextending in a circumferential direction are formed on the tips theteeth 124 which partition the slots 125, and a mutual interval in thecircumferential direction between the center of air gaps of adjacentslot opening portions 127 is varied by long and thin projections 124 aand short projections 124 a.

[0045] The mutual interval in the circumferential direction between thecenter of air gaps of adjacent slot opening portions 127 is formed byrepeating 24 degrees and 36 degrees of electrical angle. Hence, as shownin FIG. 6, wound two sets of three phase stator coils have a phasedifference of 36 degrees of electrical angle.

[0046] By making the interval in the circumferential direction betweenthe center of air gaps of adjacent slot opening portions 127 an uneven,repeated interval of 24 degrees and 36 degrees, as shown in FIG. 11,compared to the conventional example where the electrical angle is 30degrees, 5^(th), 7^(th), 11^(th), and 13^(th) higher harmonic componentsof magnetomotive force in the stator 8, which is a magnetic flux densitywave form, are lowered with good balance.

[0047] Moreover, generally the upper tolerance limit of these higherharmonic components is preferably set at around 13% in order to preventoccurrence of a noise which is unpleasant for passengers. Consequently,if the interval in the circumferential direction between the center ofair gaps of adjacent slot opening portions 127 is in the range of froman uneven, repeated interval of 16 degrees and 44 degrees to an uneven,repeated interval of 29 degrees and 31 degrees, advantageous effects canbe obtained.

[0048] Furthermore, if the interval in the circumferential directionbetween the center of air gaps of adjacent slot opening portions 127 isin the range of from an uneven, repeated interval of 22 degrees and 38degrees to an uneven, repeated interval of 24 degrees and 36 degrees,the upper tolerance limit of the higher harmonic components may be setat around 8%. That is to say, 5^(th), 7^(th), 11^(th), and 13^(th)higher harmonic components may be lowered with good balance.

[0049] Also, the stator core 122 having a plurality of small thin teeth124 in a plurality of slots is not (formed as) a conventional one-piecetubular object but is shaped from a laminated rectangular bodyrectangular into a cylindrical shape via a manufacturing process. Hence,mounting of the stator coils on the stator core is facilitated and thequality of the product may be improved while at the same time loweringthe cost.

[0050] Moreover, although the stator core 122 according to the presentinvention is made into a cylindrical shape from a rectangular body, itis not necessarily limited to a rectangular body and as long as the slotopening portions 127 are in an expanded state when mounting the statorscoils, the effects can be achieved. For example, similar effects can beachieved by preparing a plurality of circular shapes with a largecurvature which are then combined and connected while reducing theradius of curvature.

[0051] Embodiment 2

[0052]FIG. 7 is an enlarged view of an essential portion of a statorcore showing another example of the stator for a automotive alternatoraccording to the present invention. In a stator core 222 according tothe present invention, adjacent teeth 224 are formed with uneven widths.Slots 225 have approximately the same widths, and an interval in thecircumferential direction between the center of air gaps of adjacentslot opening portions 227 is an uneven, repeated interval of 24 degreesand 36 degrees.

[0053] Accordingly, projections 224 a extending in a circumferentialdirection formed in slot opening portions 227 may be formed in the sameshape. Consequently, similar effects may be obtained without forming thelong and thin projections and short projections provided in Embodiment1.

[0054] Furthermore, in the present embodiment, a wide tooth 224 isdivided in a circumferential direction by substantially orthogonalsurfaces 224 b. These surfaces 224 b serve as contact surfaces whenconnecting a stator core 224 as an annular shape. The stator core 224 ofan annular shape is produced by welding these surfaces 224 b. Hence, astator core 222 may be obtained in which the function of the contactsurfaces 224 b is facilitated, the connecting operation is simplified,and joining properties are thereof are high.

[0055] A stator for an automotive alternator according to the presentinvention is provided wherein,

[0056] in an automotive alternator including:

[0057] the stator including, a stator core in which a plurality of slotsextending in axial directions are formed at an inner circumferencethereof and two sets of a three-phase stator coils which are fitted intothe slots;

[0058] and a rotor provided inside the stator so as to be capable ofrotating, including, a rotor coil for flowing a current to generatemagnetic flux, and a pole core for housing the rotor coil and forming aplurality of claw-shaped magnetic poles in accordance with magneticflux, and,

[0059] 2 slots are provided for each phase of stator coils and eachmagnetic pole and the total number of the slots is 72 or more,

[0060] the stator core is such that a plurality of sheet-shaped magneticmembers with a plurality of teeth patterning the slots at one side of ayoke are laminated, the stator coils are disposed in the slots, and thestator core is rounded such that the stator coils become the inner sidethereof and both end surfaces thereof are contacted to connect thestator core in an annular shape. Thus, since the stator core is dividedwhen the stator coils are inserted therein, the installationcharacteristics thereof are improved.

[0061] Also, the mutual intervals in the circumferential directionbetween the center of air gaps of adjacently formed slot openingportions are formed to be uneven. Thus, because the stator core isdivided, the mutual intervals can be made with high precision even whenthey are uneven and the stator core has a low rigidity.

[0062] Moreover, the interval of slot opening portions is a repeatedelectrical angle of α degrees and (60−α) degrees, and α degrees is inthe range of from 16 to 29 degrees. Thus, 5^(th), ₇ih, 11^(th), and13^(th) higher harmonic components may be lowered with good balance andreliability may be improved.

[0063] Also, the interval of slot opening portions is a repeatedelectrical angle of α degrees and (60−α) degrees, and a degrees is inthe range of from 22 to 24 degrees. Thus, 5^(th), 7^(th), 11^(th), and13^(th) higher harmonic components may be lowered with further goodbalance

[0064] Further, the interval of slot opening portions is a repeatedelectrical angle of 24 degrees and 36 degrees. Thus, 5^(th), and 13^(th)higher harmonic components may be lowered as best as possible andreliability is improved.

[0065] Moreover, projections extending in a circumferential directionare formed on tips the teeth which partition the slots, and a mutualinterval in the circumferential direction between the center of air gapsof adjacent slot opening portions is varied by projecting lengths of theprojections. Thus, the desired structure may be easily achieved withoutadditional components or large design changes.

[0066] Also, the widths of the teeth which partition the slots areuneven. Thus, the desired structure may be easily achieved withoutproviding the protrusions of different lengths.

[0067] Furthermore, the contact surfaces of the stator core connected asan annular-shape are formed by dividing a wide tooth among the teeth ofuneven widths in a circumferential with a substantially orthogonalsurface. Thus the contact surfaces may be easily formed even when theteeth are thin due to a large number of slots.

What is claimed is:
 1. A stator for an automotive alternatorcharacterized in that, in an automotive alternator comprising: saidstator comprising, a stator core in which a plurality of slots extendingin axial directions are formed at an inner circumference thereof and twosets of three-phase stator coils which are fitted into said slots; and arotor provided inside the stator so as to be capable of rotating,comprising, a rotor coil for flowing a current to generate magneticflux, and a pole core for housing the rotor coil and forming a pluralityof claw-shaped magnetic poles in accordance with magnetic flux, and, 2slots are provided for each phase of said stator coils and each magneticpole and the total number of the slots is 72 or more, said stator coreis such that a plurality of sheet-shaped magnetic members with aplurality of teeth patterning said slots at one side of a yoke arelaminated, said stator coils are disposed in said slots, and said statorcore is rounded such that said stator coils become an inner side thereofand both end surfaces thereof are contacted to connect said stator corein an annular shape.
 2. A stator for an automotive alternator accordingto claim 1 characterized in that, a mutual interval in thecircumferential direction between a center of air gaps of adjacentlyformed slot opening portions is formed to be uneven.
 3. A stator for anautomotive alternator according to claim 2 characterized in that, saidinterval of slot opening portions is a repeated electrical angle of αdegrees and (60−α) degrees, and said α degrees is in a range of from 16to 29 degrees.
 4. A stator for an automotive alternator according toclaim 2 characterized in that, said interval of slot opening portions isa repeated electrical angle of α degrees and (60−α) degrees, and said αdegrees is in a range of from 22 to 24 degrees.
 5. A stator for anautomotive alternator according to claim 2 characterized in that, saidinterval of slot opening portions is a repeated electrical angle of 24degrees and 36 degrees.
 6. A stator for an automotive alternatoraccording to claim 1 characterized in that, projections extending in acircumferential direction are formed on tips said teeth which partitionsaid slots, and a mutual interval in a circumferential direction betweena center of air gaps of adjacent slot opening portions is varied byprojecting lengths of said projections.
 7. A stator for an automotivealternator according to claim 1 characterized in that, widths of saidteeth which partition said slots are uneven.
 8. A stator for anautomotive alternator according to claim 7 characterized in that,contact surfaces of said stator core connected as an annular-shape areformed by dividing a wide tooth among said teeth of uneven widths in acircumferential direction with a substantially orthogonal surface.